"Choosing to remove a tab will cause an ItemEvent of type 'remove' to
be launched. This event can be listened for on a showDetailItem using
the itemListener attribute. It is up to the developer to handle this
event and code the actual removal of the tab. This is because of the
dynamic nature of the panelTabbed component, which may have dynamic
children. This also allows a finer level of control by the developer,
who can then choose a custom implementation that may (for example)
include warning dialogs, and control of which tab gains focus after a
tab is removed."

This apparently works with logic written in Java saved on the server. A question on OTN was how to handle or intercept this remove event on the client side using JavaScript. This information - unfortunately - is a bit hidden in our documentation and you have to look into the JavaScript documentation for this.

If there is an AdfItemEvent that fires on the ADF Faces client side, then there also must be a configuration available on the af:clientListener to listen for such an event. And there is (just not obvious)